I would suggest a climb up Angeles Crest.
This link is not from one of my rides (it starts in Pasadena) - but it shows the area. Getting to Angeles Crest from Glendale is pretty easy and doesnt add many miles (either take Colorado to Linda Vista up to Foothil to hwy 2 or from downtown Glendal take Glendale Ave to Verdugo, to Foothill to hwy 2).
Pasadena/Angeles Crest in Pasadena, CA | MapMyRide
Griffith Park area has some decent riding areas - Map my Ride lists the varius routes. I have only done it a few times, so hopefully someone else can provide better guidance than I can.
If you can easily drive somewhere and then ride, you may want to consider riding in the Calabassas/Malibu Canyon areas. Not too far from Glendale, but far enough that you will need to drive. Lots of great up and down sections and ocean views